1. Field of the Invention
The present invention relates to a method for producing a fuse element made of different kinds of metal and used specifically in the principal part of a fuse and to a fuse element produced with the method.
2. Description of the Related Art
A method for producing a fuse element made of different kinds of metal is disclosed in, for example, Japanese Patent Unexamined Patent Publication No. Hei. 3-102729. As shown in FIG. 4(A), a tape-like through-lay type composite material 5 is used in the method in Hei. 3-102729. The tape-like through-lay type composite material 5 comprises a fuse alloy 1 arranged in the center of the material 5 and copper 3 arranged on both sides of the fuse alloy 1 as a lead piece. Window holes 7 are bored at predetermined intervals in the longitudinal direction of the tape-like through-lay type composite material 5 so that the fuse alloy 1 can have a predetermined volume, then a material 9 is obtained as shown in FIG. 4(B). Next, as shown in FIG. 4(C), a part of the fuse alloy 1 in the material 9 is sealed up with epoxy resin 11. Finally, as shown in FIG. 4(D), the material 9 is cut with a press accordingly at an even interval in the longitudinal direction, then a fuse 13 is obtained.
Nevertheless, the method of producing the aforementioned fuse element makes it essential to use the tape-like through-lay type composite material as a stock. In order to obtain the tape-like through-lay type composite material, copper as a lead piece is welded by electron-beam onto both the lateral sides of the fuse alloy disposed in the center of the fuse element. The electron-beam welding generally requires a vacuum chamber because a heat source is energy derived from the high-speed electron beams generated in a vacuum. Therefore, as well as production facilities for them, such fuse elements costs much. On the other hand, non-vacuum electron-beam welding machines is developed and makes welding operation possible under the atmospheric pressure. However, the non-vacuum electron-beam welding machines requires attention to protect against X-rays.
In addition, electron-beam welding tends to cause porosity in products because the rate of solidification in the weld is high, which results in making bubbles hardly escapable from the fusion-welded portion. Another problem still arises from the formation of unevenness within the boundary between the different kinds of metal if a density of the beam energy is unstable. Therefore, these undesirable factors have made it difficult to obtain high-precision fuse elements.